Field
The present disclosure relates to a liquid crystal display (LCD) and a dimming control method thereof.
Discussion of the Related Art
Liquid crystal displays (LCDs) have been used in portable computers such as notebook computers, office automation instruments, audio/video devices, indoor/outdoor advertisement display devices, and the like. LCD devices display an image using a thin film transistor (TFT) as a switching element. Transmissive LCDs (or backlit LCDs), which are the majority of LCDs, display an image by controlling an electric field applied to a liquid crystal layer to modulate light incident from a backlight unit.
In an LCD device, a pixel receives a data voltage in synchronization with a gate pulse and charges the same in the pixel capacitor during a scan period. Also, the pixel is designed to output brightness corresponding to the voltage charged in the pixel capacitor during the scan period throughout 1 frame period. Since the pixel receives the data voltage during its scan period in each frame period, it holds the charged data voltage during about 1 frame period. During the holding period in which the pixel maintains the charged voltage, the charged voltage in the pixel is lowered due to a leakage current, or the like, and as a result, brightness displayed by the pixel may change during the holding period.
In particular, when the driving frequency of a display panel is low, a variation in brightness during the holding period further increases. This is because the holding period is lengthened when the display panel is driven at a low frequency as illustrated in FIG. 1. For example, when driving frequency is 60 Hz, 1 frame, which includes the scan period and the holding period, corresponds to 1/60 seconds, and thus, each pixel receives its next data voltage after 1/60 seconds. However, as illustrated in FIG. 1, when driving frequency is 20 Hz, each pixel is scanned during the first field corresponding to 1/60 seconds, and then receives its next data voltage during the fourth field that is after the second and third fields corresponding to 2/60.
As a result, when a display device is driven at a low frequency, a variation of brightness during the holding period may increase, and a flicker phenomenon may also occur due to difference in brightness at the time when pixels charge their next image data.